As the only remaining unbeaten team in the NFL, the Chiefs reach the halfway point of their season Sunday as the talk of the league. Surely, Chiefs chairman Clark Hunt could not envision his team starting 7-0 even after the organization made moves at head coach, general manager and quarterback that changed the face of the franchise: The Chiefs, who were an unsightly 2-14 last year, weren’t alone in making substantial changes after finishing at the bottom of their division in 2012. The Cleveland Browns, who visit Arrowhead Stadium on Sunday, and the Buffalo Bills, whom the Chiefs visit next week, faced the same dilemmas at head coach, general manager and at quarterback. Starting with firing their head coaches last New Year’s Eve, these three teams took different routes in making changes at the three most important jobs in a football franchise.